Higher HDL cholesterol levels are associated with increased markers of interstitial myocardial fibrosis in the MultiEthnic Study of Atherosclerosis (MESA)

Emerging research indicates that high HDL-C levels might not be cardioprotective, potentially worsening cardiovascular disease (CVD) outcomes. Yet, there is no data on HDL-C's association with other CVD risk factors like myocardial fibrosis, a key aspect of cardiac remodeling predicting negative outcomes. We therefore aimed to study the association between HDL-C levels with interstitial myocardial fibrosis (IMF) and myocardial scar measured by CMR T1-mapping and late-gadolinium enhancement (LGE), respectively. There were 1863 participants (mean age of 69 years) who had both serum HDL-C measurements and underwent CMR. Analysis was done among those with available indices of interstitial fibrosis (extracellular volume fraction [ECV]; N = 1172 and native-T1; N = 1863) and replacement fibrosis by LGE (N = 1172). HDL-C was analyzed as both logarithmically-transformed and categorized into < 40 (low),40–59 (normal), and ≥ 60mg/dL (high). Multivariable linear and logistic regression models were constructed to assess the associations of HDL-C with CMR-obtained measures of IMF, ECV% and native-T1 time, and myocardial scar, respectively. In the fully adjusted model, each 1-SD increment of log HDL-C was associated with a 1% increment in ECV% (p = 0.01) and an 18-ms increment in native-T1 (p < 0.001). When stratified by HDL-C categories, those with high HDL-C (≥ 60mg/dL) had significantly higher ECV (β = 0.5%, p = 0.01) and native-T1 (β = 7 ms, p = 0.01) compared with those with normal HDL-C levels. Those with low HDL-C were not associated with IMF. Results remained unchanged after excluding individuals with a history of myocardial infarction. Neither increasing levels of HDL-C nor any HDL-C category was associated with the prevalence of myocardial scar. Increasing levels of HDL-C were associated with increased markers of IMF, with those with high levels of HDL-C being linked to subclinical fibrosis in a community-based setting.


Results
A total of 1863 participants (49% men, mean 69 years) had available HDL-C measurements and had undergone CMR analysis for myocardial fibrosis.ECV quantifications were available in 1172 participants, while native T1 analysis was available in 1863 participants.The study population was 48% White, 14% Chinese, 21% Black, and 15% Hispanic ethnicity.Forty participants with MI events were included in the primary analyses and then excluded in the multivariate analysis model 4. The mean HDL-C level was 55 ± 16 mg/dL, with 267 (14%) participants having low HDL-C (< 40 mg/dl), 988 (53%) with normal HDL-C levels (40-59 mg/dL), and 608 (33%) participants with high HDL-C levels.The mean ECV was within normal limits (27 ± 3), as was the native T1 time (970 ± 46) 19 .Other characteristics of the study cohort are shown in Table 1.
Table 2 shows the relationship between CMR markers of myocardial fibrosis and log HDL-C.In the regression analyses, log HDL-C was positively associated with both ECV% and native T1 time in the unadjusted and other adjusted analyses (all p < 0.05).
Table 3 further displays adjusted results for the association of ECV and native T1 with HDL-C after dividing HDL-C into categories (low, normal, and high) with normal levels of HDL-C as reference.In the fully adjusted model, only participants in the high HDL-C category were associated with increased markers of IMF (both ECV [β = 0.5 ± 0.2, p = 0.01] and native T1 time [β = 7 ± 3, p = 0.01]).Even after excluding participants with MI events, only those in the high HDL-C category were positively associated with markers of diffuse cardiac fibrosis.
Tables 4 and 5 show the association between HDL-C and prognostic levels of ECV and native T1 at more than or equal to 30% and 955 ms, respectively.As a continuous variable, HDL-C was positively associated with a higher risk of ECV% ≥ 30% in an unadjusted and mildly adjusted model, but that association became insignificant in a fully adjusted model.However, HDL-C remained significantly positively associated with a higher risk of native T1 time ≥ 955 ms in all models (Table 4).The same relationship was observed when HDL-C was stratified into categories, with the association being significant only among those with HDL-C levels (Table 5).
Further subgroup analysis was done after stratifying by sex (Supp Tables 1-4).Among men, increasing levels of HDL-C were associated with higher native T1 times (Supp Table 3).This association was most significant among those in the high HDL-C category.Among women, increasing levels of HDL-C were associated with native T1 time ≥ 955 ms (Supp Table 2).
When analyzing the association between HDL-C categories with blood native T1 time, participants with high HDL-C were associated with a significantly higher native blood T1 time in an unadjusted and mildly adjusted analysis (Supp Table 5).However, this association loses significance in a fully adjusted model.
One thousand one hundred seventy-two participants underwent LGE for assessment of myocardial scar.A total of 106 participants (9%) with myocardial scar (15% men, 2% women) were identified.When analyzing the association between HDL-C and myocardial scar, there was no significant association between HDL-C or any of the HDL-C categories with the prevalence of myocardial scar in adjusted models (Tables 6 and 7).

Discussion
In our study, we evaluated the relationship between HDL-C levels with IMF, defined as an increase in native T1 time and ECV percentage, and the prevalence of myocardial scar in a population initially recruited without previous CV conditions.We now show that higher HDL-C levels were positively associated with greater ECV% and native T1 time (Fig. 1).When stratifying HDL-C groups into low, reference, and high categories, our analysis further supported the assessment that high HDL-C is associated with subclinical fibrosis by CMR.
In a previous study, Rosmini et al. studied the effect of blood composition on T1 mapping in a cohort of 77 healthy individuals 6 .They concluded that there was a positive correlation between HDL-C levels and native T1 time in the blood 7 .Given that myocardial and blood T1 are closely correlated, our results support a similar conclusion, specifically that higher HDL-C was associated with increased myocardial native T1 and ECV on the population level.However, in our study, interestingly, native blood T1 time was not associated with HDL-C after adjusting for confounding variables, highlighting a potentially different mechanism between HDL and myocardial T1 analysis.Various conditions affect native T1 values of the myocardium, which will also be reflected in the   13 .On the other hand, lower values of T1 are seen in adipose tissues due to slower-moving protons and, thus, shorter T1 recovery time 13 .One explanation for the observed results would be that elevated HDL-C levels affect the relaxation time of nearby photons and therefore affect the native T1 time, similar to the paramagnetic effect of iron in the hemoglobin on T1 relaxation time 14 .Nevertheless, we observed that high HDL-C levels were associated  9,15,16 .A previous analysis from MESA found an ECV and native T1 cutoffs of 30% and 955 ms, respectively, were linked to worse cardiovascular events and mortality 9 .Similar results were observed from the UK Biobank that elevated levels of native T1 were associated with all-cause mortality, worse cardiovascular diseases, and events 12 .However, further work will be needed to elucidate whether the association above reflects a causal contribution of HDL-C in the development of myocardial fibrosis or whether elevated HDL-C levels falsely elevate CMR markers of myocardial fibrosis by affecting T1 relaxation time 7 .
To date, large randomized controlled trials that evaluated drugs such as niacin and treatment that inhibit the cholesterol ester transfer protein such as Torcetrapib have failed to show any signs of efficacy in increasing HDL-C in preventing cardiovascular events [17][18][19] .Moreover, there is growing evidence in the literature suggesting that elevated HDL-C levels may not offer cardiac protection as previously thought 20 .Several large cohorts found an increased risk of cardiovascular disease with high levels of HDL-C, similar to low levels of HDL-C 20 .A recent study that included two prospective cohorts, the UK and Emory Cardiovascular Biobank, found that compared with those with 40 to 60 mg/dL HDL-C levels, individuals from the Emory Cardiovascular Biobank with very high HDL-C levels (> 80 mg/dL) had a higher risk of all-cause death (1.96 HR, 95% CI 1.42-2.71,P < 0.001) and cardiovascular death (1.71 HR, 95% CI 1.09-2.68,P = 0.02) after adjusting for confounding factors.Similar results were observed in the UK Biobank and after adjustment of HDL-C genetic risk scores 4 .In another prospective cohort of more than 100,000 participants from the Copenhagen City Heart Study and the Copenhagen General Population Study in Denmark, there was a U-shaped relationship between HDL-C and risk of all-cause mortality, with the high risk being found among low and very high levels of HDL-C 5 .This association was similar in both men and women.Our research findings suggest a potential link between both lower and higher levels of HDL-C and an increased prevalence of myocardial scar.Specifically, individuals with lower HDL-C levels exhibited a slightly elevated risk (OR 1.1, 95% CI 0.58-2.21),while those with higher HDL-C levels demonstrated a moderately increased risk (OR 1.5, 95% CI 0.81-2.89),compared to those with normal HDL-C levels.However, it's important to note that these associations did not reach statistical significance in our analysis.
Our current study found that increased HDL-C was associated with markers of IMF irrespective of sex.However, when stratified by sex, we found that the association was more evident in men; however, an increase in HDL-C was also associated with a significant increase in native T1 in women.Given that women have higher levels of HDL-C, this could be one of the reasons underlying the baseline elevation of IMF markers compared with men 4,10 .
Another potential theory behind the increase in markers of IMF among those with high HDL-C includes a "loss of function" or "dysfunction" of HDL-C 20 .HDL dysfunction has been found to decrease the ability to promote cholesterol removal from macrophages, prevent LDL oxidation, and control apoptosis, nitric oxide production, monocyte chemotactic protein-1, and vascular cell adhesion molecule expression in endothelial cells.Patients with altered HDL were found to have suppressed nitric oxide production through interaction with LOX-1, TLR2, and TLR4 receptors 20 .This leads to the phosphorylation of inhibitory sites in eNOS instead of activating sites 21 .
Other causes were linked to the inflammatory markers of the lymphocyte activation gene-3 (LAG-3).Prospective cohorts have found that a decrease in plasma LAG3 protein was one of the causes of the elevation of HDL-C, which was then associated with an increased risk of coronary artery disease 22 .We recently reported that in MESA and the Framingham Heart Study (Offspring cohort) the following plasma proteins were positively associated with LAG3 and HDL-C: IGF1R [insulin-like growth factor 1 receptor], LRIG3 [leucine-rich repeats and immunoglobulin-like domains 3], and DCTPP1 [DCTP pyrophosphastase 1] whereas GFRA1 [glial cell line-derived neurotrophic factor family receptor alpha 1] was inversely associated with HDL-C 23 .Abdellatif et al. examined the role of cardiac IGF1R signaling in an aging model in male mice 24 .These investigators found that young male mice with increased IGF1R signaling exhibited superior cardiac function but this rapidly deteriorated with aging, with decreased autophagic flux and impaired oxidative phosphorylation.For LRIG3, there has been one report of impaired cardiac function and low HDL-C in Lrig3 -/-mice 25 .For DCTPP1 and GFRA1, a PubMed search did not identify any publications linking either protein with HDL-C, myocardial fibrosis, or myocardial scarring.Other possibilities include genetic variants associated with reduced expression of scavenger receptor class B type I protein (SR-BI), which leads to elevated HDL-C and MI risk 20,26 .Muthuramu et al. showed that expressing hepatic SR-BI in the liver significantly reduced cardiac dysfunction in Scarb1 -/-mice, a mouse model well-known for high HDL-C, accelerated atherosclerosis and coronary artery rupture 26 .

Limitations
Our study includes several limitations.First, this was a cross-sectional study design; therefore, a causal relationship between HDL-C and CMR measures of myocardial fibrosis cannot be determined.In addition, some factors might affect measures of interstitial fibrosis, such as iron and albumin were not available.It is not clear whether the elevated ECV and native T1 result from an increase in HDL-C or HDL -C alters native T1 time and ECV percentage in a way similar to iron and hematocrit through changes in blood T1.Nevertheless, we showed that pathologically elevated levels of ECV and native T1 were associated with an increase in HDL-C.Even though interstitial fibrosis is the most common determinant of altered T1 indices in this community population, CMR T1 mapping indices are not specific to myocardial fibrosis.A build-up of the extracellular matrix usually occurs because of increased interstitial fibrosis but may also result from edema, hypertrophy, or other cardiac infiltrative disorders.Lastly, those who declined a CMR contrast agent or were not eligible for it could have been systematically healthier than those who were eligible.Thus, temporal or selection bias could not be ruled out.However, www.nature.com/scientificreports/even after excluding participants with cardiovascular events such as MI or congestive heart failure, there was a positive relationship between HDL-C and increased CMR markers of interstitial myocardial fibrosis.Nevertheless, CMR T1 mapping and LGE are reliable and noninvasive methods for evaluating myocardial fibrosis with native T1, requiring no contrast injections.This makes it accessible to patients with impaired renal function.

Conclusion
In a large community-based population, we demonstrated a positive relationship between HDL-C and markers of diffuse cardiac fibrosis.This association seems significant only among those in the high HDL-C category.Whether this relationship reflects a pathologic state of increased inflammation in response to high HDL-C levels warrants further investigation into the mechanism behind HDL-C and its impact on CMR-T1 mapping indices. https://doi.org/10.1038/s41598-023-46811-8

Table 2 .
Multivariable association between HDL-C levels with CMR measures of interstitial myocardial fibrosis (extracellular volume fraction and native T1).Model 1: Unadjusted.Model 2: Adjusted for age, race/ ethnicity, gender, body mass index.Model 3: Adjusted for variables included in model 2, and lipid-lowering therapy, low-density cholesterol, triglyceride, use of antihypertensive medication, systolic and diastolic blood pressure, diabetes mellitus, smoking status, income, heart rate, estimated glomerular filtration rate, history of MI.Model 4: Adjusted for variables included in model 3 but excluding those with history of MI.

Table 3 .
Multivariable association between HDL-C categories with CMR measures of interstitial myocardial fibrosis (extracellular volume fraction and native T1).Model 1: Unadjusted.Model 2: Adjusted for age, race/ ethnicity, gender, body mass index.Model 3: Adjusted for variables included in model 2, and lipid-lowering therapy, low-density cholesterol, triglyceride, use of antihypertensive medication, systolic and diastolic blood pressure, diabetes mellitus, smoking status, income, heart rate, estimated glomerular filtration rate, history of MI.Model 4: Adjusted for variables included in model 3 but excluding those with history of MI.

Table 4 .
Multivariable association between HDL-C levels with CMR measures of interstitial myocardial fibrosis using a cut-off of extracellular volume fraction ≥ 30% and native T1 time ≥ 955 ms.Model 1: Unadjusted.Model 2: Adjusted for age, race/ethnicity, gender, body mass index.Model 3: Adjusted for variables included in model 2, and lipid-lowering therapy, low-density cholesterol, triglyceride, use of antihypertensive medication, systolic and diastolic blood pressure, diabetes mellitus, smoking status, income, heart rate, estimated glomerular filtration rate, history of MI.Model 4: Adjusted for variables included in model 3 but excluding those with history of MI.

Table 5 .
Multivariable association between HDL-C categories with CMR measures of interstitial myocardial fibrosis using a cut-off of extracellular volume fraction ≥ 30% and native T1 time ≥ 955 ms.

Table 6 .
Multivariable association between HDL-C levels with prevalence of myocardial scar.Model 1: Unadjusted.Model 2: Adjusted for age, race/ethnicity, gender, body mass index.Model 3: Adjusted for variables included in model 2, and lipid-lowering therapy, low-density cholesterol, triglyceride, use of antihypertensive medication, systolic and diastolic blood pressure, diabetes mellitus, smoking status, income, heart rate, estimated glomerular filtration rate, history of MI.Model 4: Adjusted for variables included in model 3 but excluding those with history of MI.

Table 7 .
Multivariablewith worse ECV and native T1 levels of 30% and 955 ms, respectively.Recent studies have shown that diffuse myocardial fibrosis evaluated by native T1 and ECV is associated with worse CVD prognosis, increased risk of congestive heart failure hospitalization, and all-cause mortality association between HDL-C categories with prevalence of myocardial scar.Model 1: Unadjusted.Model 2: Adjusted for age, race/ethnicity, gender, body mass index.Model 3: Adjusted for variables included in model 2, and lipid-lowering therapy, low-density cholesterol, triglyceride, use of antihypertensive medication, systolic and diastolic blood pressure, diabetes mellitus, smoking status, income, heart rate, estimated glomerular filtration rate, history of MI.Model 4: Adjusted for variables included in model 3 but excluding those with history of MI.Figure 1.In a community based setting, high levels of HDL-cholesterol were independently associated with increased CMR-markers of interstitial myocardial fibrosis, native T1 and ECV.Vol.:(0123456789) Scientific Reports | (2023) 13:20115 | https://doi.org/10.1038/s41598-023-46811-8www.nature.com/scientificreports/